In large patio doors or doors which are held in a large frame and adapted to slide sideways in the door opening, the door is quite often left open, and in insect-infected areas it is necessary to have a sliding screen arranged to close the opening after the sliding door has been opened.
A number of inventors have directed their attention to solving the problem of keeping the door closed, and I refer particularly to U.S. Pat. Nos. 3,160,250; 4,003,102; 4,004,372; 4,126,912; 4,301,623; and 4,300,960; as well as the German Offenlegungsschrift No. 2 001 678.
In all of these door-closing devices (some of which were adapted automatically to close a thick, heavy safety door or a fire door in an industrial installation), the closing mechanism operates on either the top or the bottom of the screen or door to be automatically closed. In large and heavy doors, this presents no problem, but in lightweight screens constructed primarily for use in patio doors or similar doors in private homes or non-institutional areas, if the screen or closing member is not pulled directly at the approximate vertical center of the door, it tends to "cock" in the frame and resists the easy sliding or closing thereof.
All of the inventions of the prior art are thus defective or impractical for use in lightweight screens or patio doors, or the like, and my invention has overcome this problem, inasmuch as the operating forces all act upon the center portion of the door, and thus permit easy sliding of the door back and forth in the horizontal upper and lower tracks which guide and hold the screen in place.